1. Field of the Invention
The present invention relates to a direct cooling type refrigerator, and more particularly to a direct cooling type refrigerator in which the contact area between an inner casing defined with a storage compartment and a temperature sensor is large so that the temperature sensor can accurately and rapidly sense a variation in the temperature of the storage compartment, thereby reliably controlling a compressor. Also, the present invention relates to a temperature sensor fixing method in such a direct cooling type refrigerator.
2. Description of the Related Art
Generally, refrigerators may be classified, in terms of their cooling systems, into a direct cooling type refrigerator, in which its inner casing defined with a storage compartment to be used as a freezing compartment or refrigerating compartment is directly cooled by an evaporator, and an indirect cooling type refrigerator, in which cold air produced in accordance with a heat exchange operation of the evaporator is supplied to the storage compartment by a cooling fan.
As shown in FIG. 1, the direct cooling type refrigerator generally includes an outer casing 2 defining the appearance of the refrigerator, an inner casing 4 arranged within the outer casing 2, and defined with a storage compartment F, and an insulator 6 interposed between the outer casing 2 and the inner casing 4. The direct cooling type refrigerator also includes a compressor 8 for compressing a refrigerant, a condenser 10 for condensing a high-pressure refrigerant gas emerging from the compressor 8 into a liquid phase, a capillary tube 12 for reducing the pressure of the refrigerant emerging from the condenser 10, an evaporator 14 for performing heat exchange with the inner casing 4, thereby cooling the storage compartment F, a temperature sensor for measuring the temperature of the inner casing 4, and a control unit for turning on the compressor 8 when the temperature sensed by the temperature sensor is not less than a first predetermined temperature, for example, 5° C., while turning off the compressor 8 when the sensed temperature is not more than a second predetermined temperature, for example, −30° C.
The temperature sensor includes a heat transfer member 18 arranged to be linearly in contact with a desired portion of the inner casing 4, and a thermistor adapted to measure the temperature of the heat transfer member 18, and to output a temperature signal corresponding to the measured temperature to the control unit.
The heat transfer member 18 is attached to a desired outer surface portion of the inner casing 4 while being covered by an aluminum tape attached to the outer surface of the inner casing 4 such that it is linearly in contact with the outer surface portion of the inner casing 4.
Now, operation of the conventional direct cooling type refrigerator having the above mentioned configuration will be described.
When the condenser 10 receives a refrigerant, which has been compressed into a high-temperature and high-pressure vapor phase, it absorbs heat from the received refrigerant, and discharges the absorbed heat, thereby changing the refrigerant into a normal-temperature and high-pressure liquid phase. Subsequently, the refrigerant condensed by the condenser 10 in such a manner is subjected to a pressure reduction process while passing through the capillary tube 12, and then performs heat exchange with the inner casing 4 while passing through the evaporator 14, thereby cooling the inner casing 4. In accordance with such an operation, the interior of the storage compartment F is maintained at a low temperature by virtue of heat exchange performed between air present in the storage compartment F and the inner casing 4, and natural convection of the air in the storage compartment F.
Meanwhile, the heat from the inner casing 4 is transferred to the heat transfer member 16, so that the heat transfer member 16 is heated. The thermistor measures the temperature of the heat transfer member 16, and sends a signal representing the measured temperature to the control unit.
When the control unit determines, based on the signal received thereto, that the temperature of the inner casing 4 is not more than the second predetermined temperature, for example, −30° C., it outputs an OFF signal to the compressor so as to stop the operation of the compressor 8. On the other hand, when the control unit determines that the temperature of the inner casing 4 is not less than the first predetermined temperature, for example, 5° C., it outputs an ON signal to the compressor 8 so as to operate the compressor 8.
In the above mentioned conventional direct cooling type refrigerator, the time taken to transfer the heat from the inner casing 4 to the heat transfer member 16 of the temperature sensor is lengthened because the heat transfer member 16 is linearly in contact with the inner casing 4. For this reason, it is impossible to rapidly control the turning-on/off of the compressor 8 in response to a variation in the temperature of the storage compartment F. Furthermore, the heat transfer member 16 of the temperature sensor may not be in contact with the inner casing 4 at a certain portion thereof. In this case, there may be problems of a degradation in temperature sensing performance and dispersion of the sensed temperature.
Moreover, the heat transfer member 16 of the temperature sensor cannot be firmly fixed because it is fixed to the aluminum tape 19 which is, in turn, fixed to the inner casing 4. For this reason, the contact between the heat transfer member 16 and the inner casing 4 may be degraded when an external impact is applied to the refrigerator.